Figure 1. Howard Atwood Kelly (1858-1943). [Gado Images/Alamy Stock Photo]

Imagine practicing medicine without computed tomography, ultrasonography, or x-ray. How accurately could you diagnose an obstructing ureteral or renal stone? In the early 1900s, the field of radiology was in its infancy. Wilhelm Conrad Röntgen would discover x-rays in 1895 and for his work, he subsequently won the first Nobel Prize in Physics in 1901. In the era before radiography, a physician’s primary tool in the diagnosis of obstructing renal and ureteral calculi was the physical exam. However, this was often not adequate. In a 1932 paper by Mathé entitled, “The diagnosis and present-day treatment of ureteral stone,” 25% of right-sided ureteral stone cases reported in this series had previously been operated on incorrectly for appendicitis or pelvic disease.¹

Howard Atwood Kelly (1858-1943) was the youngest of the “Big Four”—including William Halsted, William Osler and William Welch —founding chairs at Johns Hopkins School of Medicine (Figure 1). He was a clinical innovator, performing the first successful Cesarean section in 1888, and pioneered the use of radium in the treatment of gynecological cancer. His name is behind the Kelly clamp and he is the one identified with the test to find the ureter by stimulating its peristalsis by touching it with forceps. In Berlin in 1888, he worked with pathologist Rudolf Virchow (1821-1902) to determine the best way to catheterize ureters. Then in Prague in 1888, Czech physician Parel Pawlik showed him how to catheterize ureters using a speculum and how to conduct air cystoscopy.²

In 1901, Kelly published “Scratch-marks on the Wax-tipped Catheter as a Means of Determining the Presence of Stone in the Kidney and in the Ureter.”³ Kelly stated, “there is no other means of ascertaining the presence of calculus in the urinary tract as direct as my method of passing a wax-tipped catheter up the ureter into the kidney.” He described the preparation of the wax tip, a mixture of dental wax and olive oil, and the technique of ureteral catheterization. A diagnosis was made if scratch-marks were found on the wax tip. (Figure 2) Kelly also stated that the stone sometimes created a “grating sensation as the catheter is withdrawn,” that fragments of stone may become embedded in the wax tip, and that as “the catheter passes a ureteral stone, or enters the renal pelvis, there is often an immediate discharge of urine far in excess of possible secretion.” He further chronicled 11 cases where a diagnosis was made using the wax-tipped catheter and then verified the findings with open surgery.

Despite Kelly’s technique, a common problem that arose was inserting the wax-tipped catheter into the cystoscope without inadvertently scratching the smooth waxed tip. In 1915 Ben Kirkendall further adapted Kelly’s technique by using a loose-fitting rubber tube, which protected the wax-tipped catheter during its passage prior to ureteral cannulation.⁴ In 1926 Hugh Hampton Young, a contemporary of Kelly at Johns Hopkins, wrote that “the diagnosis of renal calculus has been made a matter of great exactness by the introduction of the x-ray and the wax-tipped catheter” in his text Practice of Urology.⁵

Young further discussed multiple methods to prepare the wax tip: (1) Kelly’s method using a mixture of 2 parts dental wax and 1 part olive oil, (2) ordinary embedded paraffin, which Young preferred, and (3) pure beeswax as per Guy LeRoy Hunner. He also discussed 3 different methods of passing the wax-tipped catheter in detail. Young believed that x-rays and cystoscopy with retrograde pyelograms should be performed for the diagnosis of urolithiasis and that if the diagnosis is still in doubt “the wax-tip catheter method of Kelly should be used.” Young concluded that “This procedure has not had the wide use it deserves.”

In 1933 Abraham Ravich published his series of 758 ureteral calculi.⁶ In Ravich’s series, 684 cases gave positive evidence of stone on x-ray film, whereas 74 were negative. Of those that were negative, 54 showed a scratch on the wax tip catheter. Ravich would write, “at times the grating noted on withdrawal of the catheter assisted in making the diagnosis. In the author’s practice, the wax-tipped catheter was as important a diagnostic measure as x-ray and in uric acid stones was often the only means whereby a diagnosis could be made.”

The meticulous skill required to perform the wax-tipped catheter technique to prevent false-positive results and the progress in radiography eventually made the technique obsolete. Howard Kelly’s wax-tipped catheter was the first reliable test to help diagnose ureteral and renal calculi prior to radiography. It would continue to have utility in diagnosing radiolucent stones until improvements in the quality of intravenous and retrograde pyelography.